Added homework file 'Exercise_1.1.ipynb' via upload

[ninakuni]

Hi Nils, my homework is enclosed in file 'Exercise_1.1.ipynb
Please let me know if something went wrong with the upload and if there's something wrong, missing or whatever :)
Thanks, Nina

[nilsvu]

Hi @ninakuni, this looks good 👍 A few things I noticed:

• You integrate only to $t=3 M$, instead of $t=10 M$
• Your light rays start at an initial coordinate distance $0 <= r0 <= 1 M$ from the black hole, which is why they all fall in (their coordinate distance decreases with time). Try starting the light ray outside the horizon $r0 >2 M$ :)
• The coordinate $r$ is only defined for positive values, so you could stop the integration once $r$ becomes negative.

[nilsvu]

Hi Nina,

• The way you changed np.linspace looks good - see how the curves go outward to increasing $r$ when you start outside of $r0=2M$? If you choose $r0$ between 1 and 3, for example, then you'll even see some curves falling in and some going out.
• To prevent $r$ from going negative, you could try to change the condition for the while loop like this:

  while r.successful() and r.t < 10. and r_history[-1] > 0:
      ...

  The r_history[-1] picks the last element from the list, which is the one that was just added in the previous iteration of the loop.

[nilsvu]

5/5 points. 💯